Such a circuit breaker is usually placed between a generator in an electricity power station and a transformer connected to a power transport line.
In known manner, the main contacts are sufficiently massive to be capable of withstanding high nominal currents without heating up excessively. They define a relatively large volume which is more difficult to put under gas pressure or into a vacuum than is a "bottle" of small size placed inside said volume. The bottle has a fixed arcing contact and a moving arcing contact which are less massive since they do not have to withstand the breaking current of the circuit breaker.
In French patent application FR 89/13279, the moving main contact and moving arcing contact extend in a common longitudinal direction, and are moved in translation parallel to said direction by pneumatic means having pistons and cylinders.
Those means are not without their drawbacks.
Firstly, it is necessary to provide electrically controlled valves to synchronize the displacements of the pneumatic actuators for the moving main contact and for the moving arcing contact. In particular, the moving main contact must accomplish sufficient displacement to withstand a transient electrical voltage prior to the moving arcing contact opening.
Secondly, at the end of the stroke of the moving arcing contact, it is not possible to obtain acceleration that is satisfactory, enabling the circuit breaker to open with great efficiency, unless relatively sophisticated apparatus is used for feeding gas to the pneumatic actuators.